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  • Using read() directly into a C++ std:vector

    - by Joe
    I'm wrapping up user space linux socket functionality in some C++ for an embedded system (yes, this is probably reinventing the wheel again). I want to offer a read and write implementation using a vector. Doing the write is pretty easy, I can just pass &myvec[0] and avoid unnecessary copying. I'd like to do the same and read directly into a vector, rather than reading into a char buffer then copying all that into a newly created vector. Now, I know how much data I want to read, and I can allocate appropriately (vec.reserve). I can also read into &myvec[0], though this is probably a VERY BAD IDEA. Obviously doing this doesn't allow myvec.size to return anything sensible. Is there any way of doing this that 1) Doesn't completely feel yucky from a safety/C++ perspective and 2) Doesn't involve two copies of the data block - once from kernel to user space and once from a C char * style buffer into a C++ vector. Any thoughts collective?

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  • Loose Coupling of Components

    - by David
    I have created a class library (assembly) that provides messaging, email and sms. This class library defines an interface IMessenger which the classes EmailMessage and SmsMessage both implement. I see this is a general library that would be part of my infrastructure layer and would / can be used across any development. Now, in my application layer I have a class that requires to use a messaging component, I obviously want to use the messaging library that I have created. Additionally, I will be using an IoC container (Spring.net) to allow me to inject my implementation i.e. either email or sms. Therefore, I want to program against an interface in my application layer class, do I then need to reference my message class library from my application layer class? Is this tightly coupling my application layer class to my message class library? Should I be defining the interface - IMessenger in a seperate library? Or should I be doing something else?

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  • How to learn to program C the right way

    - by sfactor
    i have been programming in C/C++ for my academic courses a lot and was under the impression i had a pretty good grasp of it. but lately i had to work in a bluetooth application that had a server and client implementation in a Linux box and an embedded system. i learned bluez bluetooth API, socket/network programming and coded it. however i ran into a lot of problems with memory leaks and segmentation faults and other memory related errors along the way.as the code grew more complex i all but lost control of the pointers and threads and sockets. this got me wondering that i had a lot to learn that they didn't say in the basic C/C++ books. so i wanted to ask for the resources that are available that'll help be code better in a professional way in C/C++ .especially for the Linux/Mac environment (gcc compiler).

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  • Typical tasks/problems to demonstrate differences between programming languages

    - by Space_C0wb0y
    Somewhere some guy said (I honestly do not know where I got this from), that one should learn one programming language per year. I can see where that might be a good idea, because you learn new patterns and ways to look at the same problems by solving them in different languages. Typically, when learning a new language, I look at how certain problems are supposed to be solved in that language. My question now is, what, in you experience, are good, simple, and clearly defined tasks that demostrate the differences between programming languages. The Idea here is to have a set of tasks, that, when I solve all of them in the language I am learning, gives me a good overview of how things are supposed to be done in that language. I do not know if that is even possible, but it sure would be a useful thing to have. A typical example one often sees especially in tutorials for functional languages is the implementation of quicksort.

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  • Twitter @Anywhere oauth_bridge_code

    - by AngelCabo
    I'm having trouble with Twitter's implementation of an oauth_bridge_code for the @anywhere api. I've seen a few walkthrough's on how to use this functionality but I can't seem to get the request to work for me. I'm using Ruby on Rails with the oauth gem. My code is as follows: def callback consumer = OAuth::Consumer.new(APP_CONFIG['twitter_key'], APP_CONFIG['twitter_secret'], :site => "http://api.twitter.com", :request_token_path => "/oauth/request_token", :authorize_path => "/oauth/authorize", :access_token_path => "/oauth/access_token", :http_method => :post) request = OAuth::AccessToken.new consumer json = request.post("https://api.twitter.com/oauth/access_token?oauth_bridge_code=#{params[:oauth_bridge_code]}") end I keep getting 401 unauthorized responses from the signed post request even though this is supposed to be working according to this walkthrough: http://blog.abrah.am/2010/09/using-twitter-anywhere-bridge-codes.html and a presentation from Matt Harris on slideshare. Any ideas on what I'm doing wrong (besides possibly trying to hit functionality that may not be in place)? Greatly appreciated!

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  • Working with OAuth on Google with Python

    - by Dan Loewenherz
    I'm having a very frustrating time creating a valid signature for Google's OAuth implementation. I have narrowed it all down to the fact that my signature-generation code has an error of some sort; what it is I have no idea. This is the signature base string in its entirety: GET&https%3A%2F%2Fwww.google.com%2Faccounts%2FOAuthGetAccessToken&oauth_consumer_key%3Ddlosplayground.appspot.com%26oauth_nonce%3D72815d55697cb24301fab03e1f7f1d66%26oauth_signature_method%3DHMAC-SHA1%26oauth_timestamp%3D1274327867%26oauth_token%3D4%252FX2cZ54JuseQbgRwzTBzZ7lqIwqof%26oauth_verifier%3Dihf0F2Fx%252FpnCmwbVQnk2xMre%26oauth_version%3D1.0 The OAuth Playground returns an oauth_signature of gF8qAfWjpdKjKb4KR%2FvA2Gy0vhU%3D. My code gives me ikMpIKJQJ58jseg%2BKPBTecjmYPE%3D, so obviously I'm doing something wrong. Here's my signature generation code (equivalent to that of the standard oauth.py library): binascii.b2a_base64(hmac.new(CONSUMER_SECRET, BASE_STRING, hashlib.sha1).digest())[:-1] Any thoughts?

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  • New to C# and trying to use a global variable

    - by Andrew G. Johnson
    Is it possible to use global variables in C#? I'm coming from mainly a PHP background so variables are either accessible everywhere or just a global definition away. My main issue is I have a User class that I built myself to wrap around the current users table on my company's database. I am defining it in the MasterPage but can't seem to access it from the actual pages (I don't know if there's a better word to describe them but they are the pages that inherit the styles and format from the MasterPage) Any general tips or implementation practices for me? EDIT: here's some code snippets of what I'm trying to do: Site.master.cs public partial class SiteMaster : System.Web.UI.MasterPage { public User user = new User(); } logout.aspx <%@ Page Title="" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeFile="logout.aspx.cs" Inherits="logout" %> <%@ MasterType virtualPath="~/Site.master"%> logout.aspx.cs public partial class _Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { User user = Master.user; } }

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  • Does "Value Restriction" mean that there is no higher order functional programming?

    - by Sadache
    Does "Value Restriction" mean that there is no higher order functional programming? I have a problem that each time I try to do a bit of HOP I get caught by a VR error. Example: let simple (s:string)= fun rq->1 let oops= simple "" type 'a SimpleType= F of (int ->'a-> 'a) let get a = F(fun req -> id) let oops2= get "" and I would like to know whether it is a problem of a prticular implementation of VR or it is a general problem that has no solution in a mutable type-infered language that doesn't include mutation in the type system.

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  • Core Animation bad access on device

    - by user1595102
    I'm trying to do a frame by frame animation with CAlayers. I'm doing this with this tutorial http://mysterycoconut.com/blog/2011/01/cag1/ but everything works with disable ARC, when I'm try to rewrite code with ARC, it's works on simulator perfectly but on device I got a bad access memory. Layer Class interface #import <Foundation/Foundation.h> #import <QuartzCore/QuartzCore.h> @interface MCSpriteLayer : CALayer { unsigned int sampleIndex; } // SampleIndex needs to be > 0 @property (readwrite, nonatomic) unsigned int sampleIndex; // For use with sample rects set by the delegate + (id)layerWithImage:(CGImageRef)img; - (id)initWithImage:(CGImageRef)img; // If all samples are the same size + (id)layerWithImage:(CGImageRef)img sampleSize:(CGSize)size; - (id)initWithImage:(CGImageRef)img sampleSize:(CGSize)size; // Use this method instead of sprite.sampleIndex to obtain the index currently displayed on screen - (unsigned int)currentSampleIndex; @end Layer Class implementation @implementation MCSpriteLayer @synthesize sampleIndex; - (id)initWithImage:(CGImageRef)img; { self = [super init]; if (self != nil) { self.contents = (__bridge id)img; sampleIndex = 1; } return self; } + (id)layerWithImage:(CGImageRef)img; { MCSpriteLayer *layer = [(MCSpriteLayer*)[self alloc] initWithImage:img]; return layer ; } - (id)initWithImage:(CGImageRef)img sampleSize:(CGSize)size; { self = [self initWithImage:img]; if (self != nil) { CGSize sampleSizeNormalized = CGSizeMake(size.width/CGImageGetWidth(img), size.height/CGImageGetHeight(img)); self.bounds = CGRectMake( 0, 0, size.width, size.height ); self.contentsRect = CGRectMake( 0, 0, sampleSizeNormalized.width, sampleSizeNormalized.height ); } return self; } + (id)layerWithImage:(CGImageRef)img sampleSize:(CGSize)size; { MCSpriteLayer *layer = [[self alloc] initWithImage:img sampleSize:size]; return layer; } + (BOOL)needsDisplayForKey:(NSString *)key; { return [key isEqualToString:@"sampleIndex"]; } // contentsRect or bounds changes are not animated + (id < CAAction >)defaultActionForKey:(NSString *)aKey; { if ([aKey isEqualToString:@"contentsRect"] || [aKey isEqualToString:@"bounds"]) return (id < CAAction >)[NSNull null]; return [super defaultActionForKey:aKey]; } - (unsigned int)currentSampleIndex; { return ((MCSpriteLayer*)[self presentationLayer]).sampleIndex; } // Implement displayLayer: on the delegate to override how sample rectangles are calculated; remember to use currentSampleIndex, ignore sampleIndex == 0, and set the layer's bounds - (void)display; { if ([self.delegate respondsToSelector:@selector(displayLayer:)]) { [self.delegate displayLayer:self]; return; } unsigned int currentSampleIndex = [self currentSampleIndex]; if (!currentSampleIndex) return; CGSize sampleSize = self.contentsRect.size; self.contentsRect = CGRectMake( ((currentSampleIndex - 1) % (int)(1/sampleSize.width)) * sampleSize.width, ((currentSampleIndex - 1) / (int)(1/sampleSize.width)) * sampleSize.height, sampleSize.width, sampleSize.height ); } @end I create the layer on viewDidAppear and start animate by clicking on button, but after init I got a bad access error -(void)viewDidAppear:(BOOL)animated { [super viewDidAppear:animated]; NSString *path = [[NSBundle mainBundle] pathForResource:@"mama_default.png" ofType:nil]; CGImageRef richterImg = [UIImage imageWithContentsOfFile:path].CGImage; CGSize fixedSize = animacja.frame.size; NSLog(@"wid: %f, heigh: %f", animacja.frame.size.width, animacja.frame.size.height); NSLog(@"%f", animacja.frame.size.width); richter = [MCSpriteLayer layerWithImage:richterImg sampleSize:fixedSize]; animacja.hidden = 1; richter.position = animacja.center; [self.view.layer addSublayer:richter]; } -(IBAction)animacja:(id)sender { if ([richter animationForKey:@"sampleIndex"]) {NSLog(@"jest"); } if (! [richter animationForKey:@"sampleIndex"]) { CABasicAnimation *anim = [CABasicAnimation animationWithKeyPath:@"sampleIndex"]; anim.fromValue = [NSNumber numberWithInt:0]; anim.toValue = [NSNumber numberWithInt:22]; anim.duration = 4; anim.repeatCount = 1; [richter addAnimation:anim forKey:@"sampleIndex"]; } } Have you got any idea how to fix it? Thanks a lot.

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  • Will there be IQueryable-like additions to IObservable? (.NET Rx)

    - by Jason
    The new IObservable/IObserver frameworks in the System.Reactive library coming in .NET 4.0 are very exciting (see this and this link). It may be too early to speculate, but will there also be a (for lack of a better term) IQueryable-like framework built for these new interfaces as well? One particular use case would be to assist in pre-processing events at the source, rather than in the chain of the receiving calls. For example, if you have a very 'chatty' event interface, using the Subscribe().Where(...) will receive all events through the pipeline and the client does the filtering. What I am wondering is if there will be something akin to IQueryableObservable, whereby these LINQ methods will be 'compiled' into some 'smart' Subscribe implementation in a source. I can imagine certain network server architectures that could use such a framework. Or how about an add-on to SQL Server (or any RDBMS for that matter) that would allow .NET code to receive new data notifications (triggers in code) and would need those notifications filtered server-side.

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  • c99 goto past initialization

    - by R Samuel Klatchko
    While debugging a crash, I came across this issue in some code: int func() { char *p1 = malloc(...); if (p1 == NULL) goto err_exit; char *p2 = malloc(...); if (p2 == NULL) goto err_exit; ... err_exit: free(p2); free(p1); return -1; } The problem occurs when the first malloc fails. Because we jump across the initialization of p2, it contains random data and the call to free(p2) can crash. I would expect/hope that this would be treated the same way as in C++ where the compiler does not allow a goto to jump across an initialization. My question: is jumping across an initialization allowed by the standard or is this a bug in gcc's implementation of c99?

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  • Is Boost.Tuple compatible with C++0x variadic templates ?

    - by Thomas Petit
    Hi, I was playing around with variadic templates (gcc 4.5) and hit this problem : template <typename... Args> boost::tuple<Args...> my_make_tuple(Args... args) { return boost::tuple<Args...>(args...); } int main (void) { boost::tuple<int, char> t = my_make_tuple(8, 'c'); } GCC error message : sorry, unimplemented: cannot expand 'Arg ...' into a fixed-length argument list In function 'int my_make_tuple(Arg ...)' If I replace every occurrence of boost::tuple by std::tuple, it compiles fine. Is there a problem in boost tuple implementation ? Or is this a gcc bug ? I must stick with Boost.Tuple for now. Do you know any workaround ? Thanks.

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  • How to write custom data to the TCP packet header options field with Java?

    - by snarkov
    As it is defined (see: http://www.freesoft.org/CIE/Course/Section4/8.htm) the TCP header has an 'Options' field. There are a couple of options already defined (see: www.iana.org/assignments/tcp-parameters/) but I want to come up with my very own. (For experimenting/research.) How can I get Java to write (and then read) some custom data to the options field? Bonus question: if it cannot be done with Java. what kind of application can do this? (No, I don't really feel like messing with some kernel-level TCP/IP stack implementation, I want to keep it app level.) Thanks!

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  • Choosing the non-empty Monoid

    - by Nikita Volkov
    I need a function which will choose a non-empty monoid. For a list this will mean the following behaviour: > [1] `mor` [] [1] > [1] `mor` [2] [1] > [] `mor` [2] [2] Now, I've actually implemented it but am wondering wether there exists some standard alternative, because it seems to be a kind of a common case. Unfortunately Hoogle doesn't help. Here's my implementation: mor :: (Eq a, Monoid a) => a -> a -> a mor a b = if a /= mempty then a else b

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  • Typecasting a floating value or using the math.h floor* functions?

    - by nobody
    Hi, I am coding up an implementation of Interpolation Search in C. The question is actually rather simple, I need to use the floating operations to do linear interpolation to find the correct index which will eventually be an integer result. In particular my probe index is: t = i + floor((((k-low)/(high-low)) * (j-i))); where, i,j,k,t are unsigned ints, and high,low are doubles. Would this be equivalent to: t = i + (unsigned int)(((k-low)/(high-low)) * (j-i)); Is there any reason I would actually want to use math.h floor* functions over just a simple (int) typecast?

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  • Linux - How do i know the block map of the given file and/or the free space map of the partition.

    - by Inso Reiges
    Hello, I am on Linux and need to know either of the two things: 1) If i have a regular file on some file system on a partition under Linux is there a way to know the set of the physical blocks that this file occupies on the drive from user space? Or at least the set of the file system's clusters? 2) Is there a way to get the same information about the whole free space of the given file system? In both cases i understand that if there is any possible way to extract this info it will probably be totally unsafe and racy (anything could happen to these set of blocks between the time i see them and act on them somehow). I also really don't want an implementation that will have to know a lot about every filesystem.

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  • Type problem when including tuple

    - by Person
    I'm using Visual Studio 2008 with Feature Pack 1. I have a typedef like this typedef std::tr1::tuple<std::string, std::string, int> tileInfo with a function like this const tileInfo& GetTile( int x, int y ) const. In the implementation file the function has the exact same signature (with the added class name qualifier) and I am getting a redefinition: different type modifiers error. It seems to be looking for an int& instead of a tileInfo& When I mouse over the type of the function in the header, i.e. tileInfo& it brings up a little bar saying static const int tileInfo. I think this may be the problem, but I'm not sure what to do. Any help is appreciated, thanks.

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  • CUDA small kernel 2d convolution - how to do it

    - by paulAl
    I've been experimenting with CUDA kernels for days to perform a fast 2D convolution between a 500x500 image (but I could also vary the dimensions) and a very small 2D kernel (a laplacian 2d kernel, so it's a 3x3 kernel.. too small to take a huge advantage with all the cuda threads). I created a CPU classic implementation (two for loops, as easy as you would think) and then I started creating CUDA kernels. After a few disappointing attempts to perform a faster convolution I ended up with this code: http://www.evl.uic.edu/sjames/cs525/final.html (see the Shared Memory section), it basically lets a 16x16 threads block load all the convolution data he needs in the shared memory and then performs the convolution. Nothing, the CPU is still a lot faster. I didn't try the FFT approach because the CUDA SDK states that it is efficient with large kernel sizes. Whether or not you read everything I wrote, my question is: how can I perform a fast 2D convolution between a relatively large image and a very small kernel (3x3) with CUDA?

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  • Why is my UIViewController initializer never called?

    - by mystify
    I made a view-based project from a fresh template. There's a UIViewController which is created with an XIB. In the implementation I uncommented that and added an NSLog. But this is never called: // The designated initializer. Override to perform setup that is required before the view is loaded. - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { if ((self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil])) { // Custom initialization NSLog(@"nib"); } return self; } since that is initialized from a nib / xib, that should be called for sure, right? however, it doesn't. I do get an NSLog message when I put that in viewDidLoad.

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  • Why implement DB connection pointer object as a reference counting pointer? (C++)

    - by DVK
    At our company one of the core C++ classes (Database connection pointer) is implemented as a reference counting pointer. To be clear, the objects are NOT DB connections themselves, but pointers to a DB connection object. The library is very old, and nobody who designed is around anymore. So far, nether I, nor any C++ experts in the company that I asked have come up with a good reason for why this particular design was chosen. Any ideas? It is introducing some problems (partially due to awful reference pointer implementation used), and I'm trying to understand if this design actually has some deep underlying reasons? The usage pattern these days seems to be that the DB connection pointer object is returned by a DB connection manager class, and it's somewhat unclear whether DB connection pointers were designed to be able to be used independently of DB connection manager.

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  • How to preserve object identity across different VMs

    - by wheleph
    To be specific let me illustrate the question with Spring http-remoting example. Suppose we have such implementation of a simple interface: public SearchServiceImpl implements SearchService { public SearchJdo processSearch(SearchJdo search) { search.name = "a funky name"; return search; } } SearchJdo is itself a simple POJO. Now when we call the method from a client through http-remoting we'll get: public class HTTPClient { public static void main(final String[] arguments) { final ApplicationContext context = new ClassPathXmlApplicationContext( "spring-http-client-config.xml"); final SearchService searchService = (SearchService) context.getBean("searchService"); SearchJdo search = new SearchJdo(); search.name = "myName"; // this method actually returns the same object it gets as an argument SearchJdo search2 = searchService.processSearch(search); System.out.println(search == search2); // prints "false" } } The problem is that the search objects are different because of serializaton although from logical prospective they are the same. The question is whether there are some technique that allows to support or emulate object identity across VMs.

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  • How to add response headers based on Content-type, or getting Content-type before the response is co

    - by Bozho
    I want to set the Expires header for all image/* and text/css. I'm doing this in a Filter. However: before calling chain.doFilter(..) the Content-type is not yet "realized" after calling chain.doFilter(..) the Content-type is set, but so is content-length, which forbids adding new headers (at least in Tomcat implementation) I can use the extensions of the requested resource, but since some of the css files are generated by richfaces by taking them from inside jar-files, the name of the file isn't x.css, but is /xx/yy/zz.xcss/DATB/.... So, is there a way to get the Content-type before the response is committed.

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  • Preventing EF4 ConstraintException when invoking TryUpdateModel

    - by twk
    Given following ASP.NET MVC controller code: [HttpPost] public ActionResult Create(FormCollection collection) { string[] whitelist = new []{ "CompanyName", "Address1", "Address2", ... }; Partner newPartner = new Partner(); if (TryUpdateModel(newPartner, whitelist, collection)) { var db = new mainEntities(); db.Partners.AddObject(newPartner); db.SaveChanges(); return RedirectToAction("Details/" + newPartner.ID); } else { return View(); } } The problem is with the Entity Framework 4: the example Partner entity is mapped to a database table with it's fields NOT ALLOWED to be NULL (which is ok by design - they're required). Unfortunately, invoking TryUpdateModel when some of the properties are nulls produces ConstraintException which is not expected! I do expect that TryUpdateModel return false in this case. It is ok that EF wouldn't allow set a property value to null if it should not be, but the TryUpdateMethod should handle that, and add the error to ModelState errors collection. I am wrong, or somebody screwed the implementation of TryUpdateModel method?

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  • Which SOA architecture is most appropriate for a Java application?

    - by Robert Greiner
    I am currently working on a pretty large Java 6 application where we are looking to split some of our functionality out into a service oriented architecture. It seems that the primary SOA framework for the application space is OSGi and I have been looking into Felix and Knopplerfish but I wanted to make sure that this isn't my only option. Does it make sense to use an actual web service protocol for our application like SOAP, even though we are not building a web app? Is this even acceptable? Have any of you used an implementation of OSGi (Felix, etc.) with your desktop application? if so, how did it go? Do you know of anything better? We're all pretty new to SOA here so any help would be greatly appreciated.

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  • Why am I getting "Collection was modified; enumeration operation may not execute" when not modifying

    - by ccornet
    I have two collections of strings: CollectionA is a StringCollection property of an object stored in the system, while CollectionB is a List generated at runtime. CollectionA needs to be updated to match CollectionB if there are any differences. So I devised what I expected to be a simple LINQ method to perform the removal. var strDifferences = CollectionA.Where(foo => !CollectionB.Contains(foo)); foreach (var strVar in strDifferences) { CollectionA.Remove(strVar); } But I am getting a "Collection was modified; enumeration operation may not execute" error on strDifferences... even though it is a separate enumerable from the collection being modified! I originally devised this explicitly to evade this error, as my first implementation would produce it (as I was enumerating across CollectionA and just removing when !CollectionB.Contains(str)). Can anyone shed some insight into why this enumeration is failing?

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